PriorityBlockingQueue Class in Java

The PriorityBlockingQueue class is part of the java.util.concurrent package and implements a thread-safe, priority-based blocking queue. It is similar to the PriorityQueue, but it supports operations for blocking threads, such as take() and put() which are not available in PriorityQueue.

• Thread-safe and supports concurrent access
• Elements are ordered by priority, not insertion order
• Can block threads when the queue is empty or full
• Allows custom prioritization via a comparator or natural ordering

Example: This example demonstrates adding elements to a PriorityBlockingQueue and printing the queue, which displays the elements in their internal order, not necessarily the order they were added.

// Adding elements to priorityBlockingQueue
import java.util.concurrent.PriorityBlockingQueue;

public class Geeks {
    public static void main(String[] args) {
        
        // Create a PriorityBlockingQueue
        PriorityBlockingQueue<Integer> q 
        = new PriorityBlockingQueue<>();

        // Add elements to the q
        q.add(10);
        q.add(5);
        q.add(20);
        q.add(1);

        System.out.println("PriorityBlockingQueue: " + q);
    }
}

PriorityBlockingQueue: [1, 5, 20, 10]

PriorityBlockingQueue Hierarchy

The below diagram demonstrates the class and interface hierarchy of PriorityBlockingQueue, showing its relationships with Queue, BlockingQueue, AbstractQueue and AbstractCollection.